1. Field of the Invention
The present invention relates to a process for cooling hot fired products in a kiln, which enables
products such as tiles or the like to be rapidly and safely cooled after being fired in a kiln such as a tunnel kiln or a periodic kiln.
2. Description of the Prior Art
For example, in a tunnel kiln for the firing tiles, cooling of fired products as they travel is usually effected by uniformly blowing a cooling gaseous fluid to hot fired products on trucks, from cooling nozzles arranged on the side, etc. of a cooling zone. However, it has been found that when a drastic cooling or quenching is effected to hasten the cooling, only the surfaces of the fired products are quenched rapidly, forming a sharp temperature gradient between the central portion and surfaces of the fired products making the products liable to fracture, i.e., so-called , due to dunting the thermal stresses. The cooling rate has therefore a limit, and accordingly conventional tunnel kilns have had to be provided with a relatively long cooling zone conjoined with a firing zone, for example, cooling zones as long as 40-50% of the entire length of the kiln, so that a heating schedule has been required such that trucks advance slowly, taking about 20 hours to pass through a kiln of an entire length reaching 50-100 m. Further, in the case of periodic kilns since rapid cooling is not permitted, fired products have to be retained in the kiln for a long period of time, so that the kilns generally have an extremely low productivity.